Lifting-jack.



J. B. SMYTHB.

LIFTING JACK.

APPLI'OATIO NFILBD'JUHE10,1911. I

Patented Mar. 5, 1912.

i' Wdnsses:

..1 wd V srarns PATENT onirica.

TGSEPH B. SMYTHE, 0F COATIGOQK, QUEBEC, CANADA.

Lumine-JACK.

Speciication ofLetters Patent.

Patented Mar. 5, 191e.

'Application filed June 10, 1911. SeriaLNo. 632,511.

are known as ratchet serewjacks, and has for its object the provision of a means whereby the movable member is preventedf fi'om being accidentally loivered inder a heavy load.

The invention consists in providing the edge of the bottom plate with a plurality ofratchet teeth and surrounding said bott-oni plate with a ring carrying spring pressed paw'ls adapted to engage said ratchet teeth and in inclosing thisring with a split friction band anchored inthe movable member, one end of said band being adapted to be moved towardthe other by means of a screw or similar device to vary the fiictional contact between said band and ring.

The `invention consists in certain novel features of construction and arrangement of parts which will be readily understood b v reference to the description of the drawings and to the claims hereinafter given.

Of the drawings: Figure 1 represents av vertical section of a lifting jack embodying the features of theV present invention. the cutting plane being in line 1 1 on Fig. 2.

. Fig. 2 represents a'horizontal section ofthe same, the cutting plane being on line 2-2 on Fig. `1. Fig. 3 represents an elevation of a portion of the ring inclosing the bottom plate and showing one of the spring pressed*- `pau/ls therein, and Fig. 4 represents a horizontal section of the saine, the cutting plane being on line 4 4 on Fig. 3.`

Similar characters designate like parts throughout the several figures of the draw*` in s. i

` iin the drawings, 1() represents suitable base supporting a stationary standard llover the outer periphery of which is fitted amov# able sleeve or member 12, to the uppei' end of which is threaded a head 13. ln the upper end of the standard 11 is Vmounted a non-'revoluble nut 14, to which is threaded a with said gear.

lifting screw 15, having splined to its upper reduced end a gear 16, with which meshes a gear 17 formed upon or secured to a revoluble shaft 18, the outer end of which is provided with a suitable operating mechanism 19 of any Well-known construction. Interposed between the upper face ofthe gear 16 and theinner face of the head 413 are tivo annu- ]ar plates 20 and 21, between which are interposed a plurality of. anti-fnic'tion mem# bers 22. Between the plate,21 and the upper face of the gear 16 is preferably positioned'a friction disk 23. V'The bottom plate 21 is provided with 'a plurality' of ratchet teeth` 24 with which engage `the pawls 25 pivotally mounted in aring 26 surrounding said bottoni plate 21 and forced Iinto enga-gement with said teeth 24 by means of suit-able springs 25". It is obvious that when thehandle-27 of the shaft operating mechanism 19 is operatedv to move the gear in the direction of the arrow indicated on Fig'. 2 of the drawings, the screivl will beso turned in the nut 14 as to cause "the member 12 to be lifted relative to the standard 11, and during this rotation of the gear 1.6 thel friction be- 'l tween the plate 21 and said `gear 16 caused by the inteiposition of the friction disk 23 will be such as to cause the-'plate 21 to rotate The ratchet teeth 24 on the lower plate 21 are soiconstr'uttled that during this movementthe lower plate 21, gear 16,

and screw 15, will allturn together freely,

the pawls 25 being forcedintotheir recesses against the tension of the spring 25* as the toothed plate 21 revolves, the ring` 26 being prevented from moving by the friction band 28 surrounding its` periphery and contacting therewith. This friction band 28 is provided vvith a lug 29 positioned 'in the recess in the inner ,Wall of the casing of the member 12, and` diametrically opposite this lug the `band is split .and provided with two outwardly extending lugs 30 also positioned in a recess in the inner Wall of said movable member 12. `When the `inner Wall of the.

band 28 is in normal contact with 'the periphery of theV ring 26, the lugs are slightly separated.

Threaded to the casing of the movable member l2 is a threaded member 31, the inner end of Which bears against one of the lugs 30. It is obvious that by turning this i threaded member 31 the ends of the band 28 may be forced toward each other, thereby making a rmer frictional contact between the band '28 and ring 26. The lugs 29 and 30 anchor the friction band and prevent any movement in either direction during the operation of the jack. l/Vhen lowering the movable member l2, the teeth 24 on the bottom plate 2l engage with the pawls 25 and v cause the ring 26 to rotate therewith, the movement'of this ring 2G being retarded to a greater or less extent in accordance with the .degree of frietional contact of the band Q8 with its periphery. The ball bearing jacks now in use have a tendency to run down when worn or when the load is jarred, but this objection is entirely overcome in the present invention by the friction between the movable band 28 and the pawl ring 26. Owing to this tendency torun down the pitch of the threads of the screw is neces sarily limited,y and as they have tc be returned to the lowest position by hand the operation is necessarily very slow. In the present invention, however, byhaving the bottom plate provided with ratchet teeth on its periphery which cooperate with the pawls carried by a ring, the movement of which is controlled by a brake band, a very rapidly moving screw may be used. Obviously, by adjusting means such as the threaded member 3l, the brake band may be either tightened sufficiently to prevent the screw from running down or locked so that no jt lring or wear can cause an accident; while, at Athe same time, a simple adjustment of the threaded member Blwill decrease the frictional contact between "dieJ band Q8 and ring QG after the load has been blocked rup or the job completed to permi't `the'screwio run down by its own'weight into r@anormal position preparatory to another lifting opera.- tion. `While a threaded member is shown in lthe drawingsto regulate the frictional 'contactbetween the band 2S and the ring 26; it is obvious that other well-lrnown devices may be used equally as well without altering the principles of the present invention.

When desired, this screw 3l. or othe adjusting device may be instantly removed from the jack-so that the jack would be inoperative, it being self-evident that the jack will not hold any load whatever without the application of some friction to the ring 2G on account of the coarse pitch usually used in a ack of this character.

It is believed `that the operation and many advantages of the invention will be thoroughl y understood from the foregoing.

Having thus described my invention, I claim: i

1. In' a lifting jack, the combination of a stationary member; a movable member thereon; a screw for said movablejmervnber; means for rotating said screw; a plate carried by said screw; a plate carried by said movable member; anti-friction members interposed between said plates; and adjust-able mechanism for creating a variable friction on said screw plate.

2. In a lifting jack, the combination of a stationary member; Va movable member thereon; a screw for said movable member; means for rotating said screw; a plate carried by said screw; a plate carried by said movable member; anti-friction members interposed between said plates; a ring surrounding saidscrew plate; means interposed between said ring and plate to insure their simultaneous movement in one direction; and a non-revoluble friction band surrounding said ring. 1

3. In a lifting jack, the combination of a stationary member; a movable member thereon; a screw for said movable member; means for rotating said screw; a plate carried by said screw; a plate carried by said movable member; anti-friction members interposed between said plates; a ring surrounding said screw plate; means interposed between said ring and plate to insure their simultaneous movement in one direction; a non revoluble friction band surrounding said ring; and means for adjusting said band to regulate its frietional contact with said ring. v

4. In a liftingA jack, the combination of a stationary member; a movable member thereon; a screw for said movable member; means for rotating said screw; a plate carried by said screw; a plate carried by said movable member; anti-friction members interposed between said plates; a vringsur rounding said screw plate; means interposed between said ring and plate to insure their simultaneous movement in one direction; a non-revoluble friction band surrounding said ring provided with projections positioned in depressions in the jack casing.

5. In a lift-ingjack, the combination of a stationary member; a movable member thereon; a screw for said movable member; means for rotating said screw; a plate carried by said screw; a plate carried by-said movable member; anti-friction members interposed between said plates; a ring surrounding said screw plate; means interposed between said ring and plate to insure their simultaneous movement in one direction; a non-revolulile split friction band surrounding said ring; and means connectii'ig the 'ends of said split band for regulating the frictionaleontact with said ring.

6. Ina lifting jack, the combination of a stationary member; a movable member thereon; a screw for said movable member; means for; rotating said screw; a plate carried by said screw; a plate carried by said movable'member; anti-friction members interposed between said plates; a ring sur- Vroux-iding scid screw p1ate;, means interposed I Sgnedfby me at 4 `Post Oice Sq., Boston, between said ring and piatte to lnsure 'their Mass., this 19th day of May, 1911.

simultaneous movement in one direction; a.

non-revoluble split friction band surround- JOSEPH B. SMYTHE. 5 ing said ring;, .and a screw 4connecting the Witnesses: 4 I

ends of'said split band for regulating the l WALTER E. L0MBARD,

frictional contact with said ring. NATHAN C..L0MBARD. 

